Service

What is the fuel pump and how does it work?

The fuel pump supplies pressurized gasoline to each of the fuel injectors in a car’s engine. The fuel pump is powered by a compact electric motor and is located in the vehicle’s gas tank. The pressure and output of the pump are controlled by a regulator. Filtration of the fuel occurs either in the fuel tank using a pickup screen or externally with a replaceable filter mounted in the fuel supply line.

When to consider replacing the fuel pump?

A high quality, OEM fuel pump can last indefinitely. However, as with any electro-mechanical component, a fuel pump will eventually degrade and fail. If it fails to produce adequate pressure or completely quits operating, it will need to be replaced. This failed condition can sometimes be preceded or accompanied by one or more of the following symptoms:

Car won’t start or unexpectedly stalls and won’t re-start. A failed fuel pump may prevent a car from starting or stall it.

Check engine light is on. Sometimes a fuel pump will fail slowly, and that means the fuel pressure and volume slowly degrades. The lack of fuel may result in the engine operating without enough fuel relative to the amount of air, causing the check engine light to appear.

Whirring noise from fuel tank. As a fuel pump fails, you may notice a whirring or humming noise coming from the fuel tank area, toward the rear of the car. If the noise is from the fuel pump, failure of the pump is often imminent and you should replace the fuel pump at your earliest convenience.

How do mechanics replace the fuel pump?

The fuel pump is tested to be sure it isn’t functioning.

Should the fuel pump be faulty, it is removed from the tank through an access panel above the tank in the passenger compartment.

When no access panel exists, fuel is first drained from the tank and then the fuel tank must be lowered from the vehicle to gain access to the pump.

In all cases, fuel pump supply and return hoses, as well as EVAP system hoses, and electrical connections to the pump must be removed.

Once the pump is out, any reusable brackets and pick up screens are attached to the new pump, then the new pump is installed.

If the fuel system uses an in-line external filter, a filter is often replaced. All hoses and electrical connections are re-established.

Fuel is added to the tank and the engine is run to test for leaks.

Is it safe to drive with a fuel pump problem?

Usually, it’s still safe to drive, but the pump may lead to an overheated engine and catalytic converter. Complete fuel pump failure can leave you stranded out on the road, but many times a car won’t start before initially driving.

However, if the fuel pump problem involves leaks of gasoline or vapors, it is unsafe to continue driving, and should immediately be checked by a qualified mechanic.

When replacing the fuel pump keep in mind:

Prior to replacing, the mechanic will power the fuel pump directly to confirm that the issue is a failed pump versus a faulty power supply to the pump.

Unless the fuel filter was replaced recently, whenever the fuel pump is replaced a new fuel filter should be installed.

When failing earlier than expected, the power supply should be verified because a voltage drop in the fuel pump circuit can lead to overheating.

Should the fuel tank be lowered during the repair, the fuel tank straps and fasteners should be checked for excessive corrosion and replaced as needed.

The fuel in the gas tank cools and lubricates the fuel pump. After installation of a new fuel pump, it’s wise to keep the gas tank at least a quarter full to maximize the life of a new fuel pump.